Selective catalytic reduction (SCR) catalysts are subject to deactivation resulting from the various conditions encountered in the exhaust aftertreatment system. For example, deactivation can result from poisoning of the SCR catalyst caused by various sulfur compounds and hydrocarbon species present in the exhaust gas as well as other deactivation conditions. Other types of catalysts in the exhaust system, such as an ammonia oxidation (AMOX) catalyst, are also subject to deactivation conditions.
In exhaust systems that include, for example, active particulate filter regeneration, the particulate filter regeneration event can serve in part as a regeneration event for the SCR catalyst and other catalysts as well. However, certain aftertreatment systems do not include a particulate filter requiring periodic regeneration. In other systems or operating conditions, the regeneration event for a particulate filter may provide insufficient exposure to regeneration conditions to provide a desired catalyst regeneration outcome. In addition, the conditions which indicate a need for particulate filter regeneration may not indicate a deactivation condition for catalyst regeneration. As a result, the catalyst may be required to operate while contaminated until a particulate filter regeneration event occurs. Therefore, further technological developments are desirable in this area.